Torque-limiting wrench



R. G. WOODS TORQUE-LIMITING WRENCH April 23, 1957 2 Sheets-Sheet 1 Filed Aug. 22, 1955 RoERT @LEN WOODS uvm/roza.,

y@ .f 1 Y 9 April 23, 1957 R. G. WOODS TORQUE-LIMITING WRENCH 2 Sheets-Sheet 2 .A

Filed Aug. 22, 19,55

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TORQUE-LIWITING WRENCH Robert Glen Woods, Huntington Park, Calif.

Application August 22, 1955, Serial No. 529,617

7 Claims. (Cl. 81-52.4)

The present invention relates generally to wrenches and more particularly to a novel torque wrench.

It is well known that torque-limiting wrenches tind wide applications in many industries. Generally, these torque-limiting wrenches include :a load-engaging member and a spring which resists the movement of the loadengaging member until Ia desired amount of torque is applied to the load thereby. The application of such limited amount of torque to the load through the loadengaging member causes the latter to break, i. e. to undergo movement from its original position to -a -second position. This breaking movement against the force of the spring provides an indication that the desired amount of torque has been applied to the load. In heretofore proposed torque-limiting wrenches the moving members are supported within the wrench by Asuitable bearing means which permit such moving members to undergo relative rotating or sliding motion. A major disadvantage of these heretofore-proposed torquelimiting wrenches results from the varying friction-a1 resistances of the moving members to such rotating or sliding motion. These varying frictional resistances eifect unavoidable inaccuracies with regard to the amount of torque required in causing the wrench to break It is a major object of the present invention to provide a novel torque wrench which is so constructed that its moving parts have very low frictional resistance against relative movement during a breaking operation.

Another object is to provide a torque wrench of the afore-described nature which atords extremely accurate results each time that it is used.

An ladditional object is to provide a torque wrench of compact size and light weight that is economical of construction.

Another object is t-o provide a torque wrench of the afore-described nature which is readily adjustable with regard to the amount of torque required to obtain a breaking movement of the load-engaging member.

Yet a further object of the invention is to provide a torque wrench that is simple of design and rugged of construction whereby it may alord a long and useful service life.

These and other objects and advantages of the present invention will become apparent from the following detailed description of a preferred and an Ialternate embodiment thereof, when taken in conjunction with the appended drawings wherein:

Figure l is a top view of a preferred form of torque wrench embodying the present invention, which view is partly broken away in horizontal section;y

Figure 2 is a fragmentary top view corresponding to Figure 1 but showing the parts of the wrench disposed in a diierent position;

`Figure 3 is a side view of said wrench, which view is partly broken away in vertical section;

Figure 4 is 'a fragmentary top view of an alternate form of wrench embodying the present invention, which view is partly broken away in horizontal section;

States Patent O Patented Apr. 23, 1957 fiCe Figure 5 is a fragmentary side view of said alternate form of wrench, which view is partly broken away in vertical section.

Referring to the drawings and particularly 'Figures l, 2 land 3 thereof, the preferred form of torque wrench embodying the present invention broad-ly comprises elongated hollow body B; a load-engaging member L which is supported in the front portion of the body `B for rotation about a vertical axis X-X; handle means H formed on the rear end of the body B; .a pivot member -P pivotally disposed within the body YB rearwardly of the load-engaging member L; a lever element E extend ing ybetween the rear of the load-engaging member L and the front of Ithe pivot member P; and a spring S interposed between the rear of the pivot member P and the rear of the body B for opposing rearward pivotal movement of the pivot member P. Torque may -be applied to an object through the load-engaging member L by moving the handle H in a clockwise direction from its position of Figure l.

,More particularly, the body B may be formed of a cover member, generally designated 10, and a base member, generally designated 12, telescopically interlitted within the cover member. Both the cover member 1@ and the base member 12 may conveniently be stamped or otherwise formed from sheet metal. The cover memn -ber 10 includes a top plate 14 and `a side wall 16 which depends from the side and front portions thereof. As shown in Figure l, the -front portion of the top plate 14 is arcuate in plan view. The rear portion of the top plate 14 is formed with a transversely extending rectangular opening 17 and a longitudinally extending slot 18 rearwardly of opening 17. The base member 12 includes a bottom plate 20 and .an opstanding side wal-l 22 formed along the `side and front portions of the bottom plate. The front portion of the bottom plate 20 is also arcuate in plan view and is formed with a bore 24. The rear portion of the bottom plate 2.9 is formed with a transversely extending rectangular opening 26 which is in vertical alignment with the opening 17 in the top plate 14. The rear end of the body B is lopen for receiving the front end of the handle H. This handle H may be rigidly secured -between the top and bottom plates 14 'and 20, respectively by pins 23.

The load-engaging member L includes a cylindrical boss 30 having a diameter somewhat smaller than the inside diameter of the front portion of the body B. A generally rectangular ear 32 integrally extends from the rear portion of the boss 30. The underside of the boss Sti is coaxially formed with a keying disc 34 that is rotatably disposed within the bore 24 formed in the front portion of the bodys bottom plate 20. A pin element 33 inte grally depends from 4the keying disc 34 for insertion with in a complementary socket (not shown) formed on an object to which a load is to be applied (also not shown). It will be understood that the pin element 33 may assume other forms without departing from the spirit of the present invention. The rear portion of the ear 32 is formed with a generally triangular notch 40. A transversely extending adjustment bolt 42 having its shank engaged with a lock nut 44 is carried by the ear 32 for a purpose to be set forth hereinafter. The pivot member P is spaced somewhat rearwardly from 'the rear end of the loadengaging member L and in horizontal alignment therewith. As shown in Figures l and 2, one end of the pivot member P is formed with a point 46 and is restrained against rearward movement by an abutment 48 formed on the side wall 22 of the base member 12. The opposite end of the pivot member P is free to pivot rearwardly from its position of Figure l to its position of Figure 2. A retainer 50 is pivotally disposed vwithin a pocket 51 formed inthe intermediate portion of the pivot member P for engagement with the front end of the spring S. The front portion of the pivot member is formed with a generally triangular notch 52.

rihe lever element E is *formed Wit-h points 54 and 56 at its opposite ends, which points Aare disposed within the apexes of the two notches 40 and 52, respectively, formed in the load-engaging member and the ypivot members, re spectively.

The spring S is of the helical compression type. The rear end of this spring is supported upon the front end of a threaded post 58, the rear coil of the spring abutting the front of a backing disc 60 secured to said post. Rearwardly of lthe backing disc et) the post 58 is threadedly engaged with a threaded bore 64 coaxially formed in an adjusting dial 6,6. The 'latter is rotatably supported relative to the body B by means of the rectangular openings 17 and 2e. ln order to provide a visual indication of the relative positions of the backing dise vll and the body B, the rear portion of the post 58 is rigidly secured to a pointer 70 having an indicator element 72 which extends through the slot 1S formed in the bodys cover member so as to key the post 58 against rotation relative to the body B. Upon rotation of the dial `66 the post 5S and hence the pointer 79 will undergo concurrent longitudinal movement along the slot 18. The cover member lo is marked with sealer markings 74 alongside the slot 13, while the .adjusting dial 66 may be marked with complementary sealer markings 76. These markings may constitute Vernier graduations reading in foot-pounds or inch-pounds and should be so coordinated with the .spring rate of the spring S and the geometry of the Wrench as to provide a visual indication of the amount of torque being applied by the load-engaging member L.

In operation, referring to Figures 1 and 2, and assuming that the load-engaging member L has been connected with a load, the rear end of the handle H is moved in a clockwise direction. During such handle movement the tendency of the load-engaging member L to rotate in a counter-clockwise direction relative to the body Vl will be resisted by the spring S through the pivot member P and the lever element E. When, however, the torque being applied by the load-engaging member reaches a pre-determined limited magnitude, the load-engaging member will break or rotate in a counter-clockwise direction about the vertical` axis X-X, the pivot member P and the lever element E pivoting from their position shown in Figure l to that of Figure 2. The abutment of the adjustment bolts lock `nut 44 with the side wall 22 of the bodys base member 12 limits the amount `of rotational movement which ma-y be undergone by the loadengaging member L. It should .be particularly noted that the pivot member P and the lever member E pivot on knife points 46, 54 and 56 when the load-engaging member breaks, and accordingly a minimum amount of friction will be developed between the 1oad-engaging mem ber and the pivot member.

lt is possible to effect a variation inthe force applied by the spring S by means of the adjustment bolt 42. In this regard, the setting of this adjustment bolt 42 controls the initial position of the load-engaging member L relative to the body B. Hence, it likewise controls the angle existing between `the lever element E and the loadengaging and pivot members. This angle in turn ldetermines the direction of thc force applied by the load- `engaging member against the pivot member during a torque applying operation before the wrench breaks Assuming the forwardly acting force applied by the spring S against the pivot vmember is constant, the greater the angle of the lever element relative to the load-engaging and pivot members, the greater the amount of torque which will be required to keiect `breaking of the wrench.

Referring now to Figures 4 and S, there is shown an alternate Vform of 'torque wrench embodying the present invention. Thisl form `of 'wrench .includes a. body .Bg a

desafiar f load-engaging member L'; a handle H; a pivot member P'; a levery element E'; and a spring S'. These vmembers generally correspond to the similar unprimed elements described hereinabove with reference to the preferred form of wrench shown in Figures l, 2 and 3. It should be noted, however, that this alternate form of wrench does not incorporate means for varying the length of the spring S. Instead, the rear end of this spring S' is received by a fixed anchoring stud formed on the front end of the handle H'.

ln this form of the invention, the amount of torque required to cause the load-engaging member L' to break is varied by means Vof van adjustment bolt 82 having its shank 83 engaged with .a threaded bore 8f4 that is formed in the bodys side walls 16 and 22. The front of the shank abuts one side of the load-engaging members ear 32. A stop element 86 is formed on the opposite side of the ear 32. Upon rotation of the adjustment bolt 82 by means of its knurled head 90, the initial position of the load-.engagingmember L' relative to the lbody B' may be controlled. lt will be apparent that in this manner the angle of the lever element E relative `to the loadengaging and pivot members will likewise be varied. As indicated hereinabove, for a given spring force the latter .angle controls the amount of torque required to effect breaking of the wrench during a torque applying operation. The head of the adjustment bolt is marked with suitable sealer markings 92 for providing a visual indication of the setting of the wrench.

While there has been shown and described hereinbefore what are presently considered to be the preferred and an alternate embodiment of the present invention, it will be apparent that various modifications and changes may be made therein without departing from the spirit of the invention or the scope of the following claims.

I claim:

l. A torque wrench, comprising: an elongate, rigid member; a load-engaging member rotatably carried at one end of said elongate member; a pivot carried by said elongate member rearwardly of said load-engaging member; resilient means mounted on said elongate member that normal-ly bias the free end of said pivot towards said load-engaging member; and a normally canted lever wedgingly engaged between the adjacent end of said loadengaging member and said pivot that resists pivotal movement of said pivot towards said load-engaging member and that moves toward alignment with said elongate member when the load on said load-engaging member exceeds the biasing force of said meanswhereby said pivot turns rearwardly.

2. A torque wrench, comprising: an elongate, rigid member; .a loadengaging member rotatably mounted at the front end kof said elongate member; a pivot element on said `elongate member extending substantially transversely thereof, said element and the rear of said loadengaging member having confronting faces and the free end of vsaid element being resiliently biased towards said load-engaging member; and a canted lever between the confronting faces of said load-engaging member-and said element that prevents pivotal movement of said element towards said load-engaging member and that tends to move into alignment with said elongate member when the load on said wrenehexceeds the biasing force on said element whereby said element yields rearwardly to permit movement of said elongate member relative to said loadeng-agingmember.

3. A torque wrench, comprising: an elongate, rigid member; .a load-.engaging member rotatably mounted on the `front .end of said elongate member that is movable through a predetermined are relative thereto; an element extending .substantially transversely of said elongate member that at one of its .ends pivotally engages said .elongate member, said element and said. `load-.engaging member being formed 'with ,confronting faces; spring means .on said elongate member normally biasing the free end of said element towards said load-engaging member; and a lever between the confronting faces of said element and said load-engaging member that is norm-ally canted out of alignment with said elongate member and prevents pivotal movement of said element towards said loadengaging member to that when the load on said wrench exceeds the biasing force of said spring means, said means yield to permit rearwardly pivoting movement of said element tending to bring said lever into alignment with said elongate member whereby said elongate member moves through said predetermined arc relative to said load-engaging member.

4. A device as set forth in claim 3 in which said wrench has means to adjust the cant of said lever to vary the breaking point of said wrench.

5. A device as set forth in claim 3 in which the opposite ends of said lever are formed with knife edges that engage complementary notches formed in the confronting faces of said load-engaging member and element.

6. A device as set forth in claim 5 in which the pivotal engagement of said element and elongate member comprises a knife edge at one end of said element that defines the pivotal axis thereof and said elongate member includes an abutment adapted to receive said knife edge and said lever engages said element intermediate its pivotal axis and the connection thereto of said spring means.

7. A device as set forth in claim 3 in which said wrench is provided with calibrated means to adjust the force of said spring means.

References Cited in the le of this patent UNITED STATES PATENTS 2,268,081 Pagnard Dec. 30, 1941 2,300,652 Cooney Nov. 3, 1942 2,662,436 Harmes Dec. 15, 1953 2,667,800 Garwood Feb. 2, 1954 2,732,747 Livermont Jan. 31, 1956 FOREIGN PATENTS 49,369 France Dec. 17, 1938 833,896 France Aug. 1, 1938 

